System Controls

The A/C-Heater Control Module:

• is fully addressable with the DRBIII®.
• communicates over the Programmable Communication Interface Multiplex System (PCI) Bus.
• provides an A/C request to the Powertrain Control Module (PCM) over the PCI Bus when compressor operation is desired.
• uses input from the evaporator temperature sensor to prevent evaporator freeze up while maintaining optimum cooling performance.
• for exports with diesel engines, provides a Cabin Heater activation request to the Front Control Module (FCM) over the PCI Bus when conditions are favorable for Cabin Heater operation.
• for RS vehicles, provides a blower relay on request to the FCM over the PCI Bus upon ignition on.
• for RG vehicles, provides a blower relay on request to the FCM over the PCI Bus when the Power switch on the A/C-Heater Control Module is turned on.
• controls front blower operating speed. For RS vehicles, the four speed settings are Low, M1, M2, and High. For RG vehicles the five speed settings are Low, M1, M2, M3, and High.
• for RS vehicles uses the blower switch to control system on/off and blower speed.
• for RG vehicles uses the power switch to control system on/off and the blower switch to control blower speed.
• for RS vehicles uses the rear wiper/washer switch to control rear wiper/washer operation.
• for RS vehicles, provides a rear wiper on request to the Body Control Module (BCM) when rear wiper operation is desired.
• for RS vehicles, provides a rear washer on request to the Body Control Module (BCM) when rear washer operation is desired.
• controls EBL operation.
• on three-zone systems, activates and deactivates the Rear A/C-Heater Control.
• on three-zone systems, controls rear blower operating speed. The three speed settings are Low, Med, and High.
• controls the front and the three-zone system rear electric door actuators' operation.
  • A simplified control system for operation of the mode, recirculation, and temperature control actuators provides positive positioning without the complexity of feedback from position sensors. The A/C - Heater Control Module knows the number of operating actuator revolutions required for full door travel as well as the number of actuator commutator pulses per revolution. Using these parameters, the A/C - Heater Control Module runs the actuator for the number of commutator pulses that correspond to the desired door position. To maintain accuracy, the system recalibrates itself periodically at known zero and full travel conditions.

On Three-Zone systems, the Rear A/C-Heater Control:

• controls rear blower motor operating speed. The three blower speeds are Low, Med, and High.
• provides desired rear blend and mode door position input to the A/C-Heater Control Module.

The Single-Zone HVAC system uses:

• one, two-wire electric blend door actuator.
• one, two-wire electric mode door actuator.
• one, two-wire electric recirculation door actuator.

The Dual-Zone HVAC system uses:

• two, two-wire electric blend door actuators.
• one, two-wire electric mode door actuator.
• one, two-wire electric recirculation door actuator.

The Three-Zone HVAC system uses:

• two front, two-wire electric blend door actuators.
• one front, two-wire electric mode door actuator.
• one, two-wire electric recirculation door actuator.
• one rear, two-wire electric blend door actuator.
• one rear, two-wire electric mode door actuator.

System Relays

• The Integrated Power Module (IPM) houses and provides power to the A/C Clutch Relay, Front Blower Motor Relay, and Rear Blower Motor Relay.